EFFICACY OF TRICHODERMA-HARZIANUM AS A BIOLOGICAL-CONTROL OF FUSARIUM-OXYSPORUM IN CONTAINER-GROWN DOUGLAS-FIR SEEDLINGS

Inoculating a soilless medium with encapsulated Trichoderma harzianum did not affect any aspect of Douglas-fir (Pseudotsuga menziesii var. g lauca [Beissn.] France) seed germination or subsequent growth. Results of inoculating medium with a known pathogenic isolate of Fusarium oxy sporum alone, or concurrently with T. harzianum, were the same: high l evels of damping-off, low amounts of hypocotyl and root disease in mid summer, and significant reductions in height growth. When seedling roo ts grew through T. harzianum-inoculated medium before growing into a m ixture of T. harzianum-F. oxysporum-inoculated medium, mortality was r educed about 50%. Although contamination by resident Fusarium occurred , subsequent root colonization was significantly reduced in T. harzian um-amended growing medium.